This invention relates to a method of preparing and preserving filled dough food products.
Filled or stuffed dough food products refer herein to those food products which comprise relatively small casings of dough, of any geometrical or fancy shapes, filled with a mixture or "emulsion" of chopped meat, vegetables, cheese, spices, etc., and are best known by their traditional names of "ravioli", "tortellini", "capelletti", "canelloni", etc.
In the case of stuffed pasta such as ravioli, tortellini, cannelloni and the like, long standing problems such as the inability to preserve the stuffed pasta in a good state for a certain period of time has been unresolved. Several processes have been developed to insure that neither the outer shell portion nor the inner stuffing which generally constitute meat, greens, cheese and other suitable stuffing, undergo deterioration between production and consumption.
The filler or filling of the above filled dough food products comprises a lump of food material such as meat, or other mixture, wrapped in a sheet of new-made dough. A special problem encountered in the instance of filled dough products is that improving the taste quality of the filler by enhancing its flavor, often brings about a deterioration of the appearance and properties of the casing formed from dough.
Known are treatments for preserving, over a short or long period of time, such filled dough food products which provided for the drying thereof (which drying process would generally continue spontaneously even after the drying treatment proper has been completed), but it is also known that this resulted in the dough casings becoming brittle, developing cracks, and finally turning to crumbles, thereby their appearance made them totally unsuitable for sale.
In conventional filled food products, such as tortellini, both the dough and the filling material commonly have 31-32% moisture by weight, and an A.sub.w of 0.92-0.97. These products are dried at 60.degree.-65.degree. C. for 18-24 hours and the finished products require 16-20 minutes cooking time.
Moreover, a deep drying treatment could damage the filler as well as the dough casing, because, as is well known in the art, dehydrated meat does not "recover" with the simple addition of water, not even boiling water. Lastly, the deep drying effect brought about by conventional preservation methods can result in an undue loss of weight.
On the other hand, deep freezing encourages cracking and disgregation of dough owing to the surface dehydration caused by the application of cold. Moreover, deep freezing involves high refrigeration costs for production distribution, and conservation.
Finally, dehydration is likely to result in the dough developing surface cracks, in the deterioration of the filler owing to the high temperatures involved, in a degradation of the flavor due to partial evaporation of spices, in an increased cost of the product due to the loss of weight brought about by the drying process and so forth.
Therefore, the methods proposed heretofore for preparing or preserving filled dough food products have failed to provide an acceptable shelf stable filled dough food product.
Limiting "water activity" (A.sub.w) in intermediate moisture foods has become an important method of preventing microbial decomposition. Water activity is the measure in a system of the unbound free water available to support biological and chemical reactions. One measure of water activity is A.sub.w =P/P.sub.o, where P is the vapor pressure of water in the system (food item) and P.sub.o is the vapor pressure of pure water a the same temperature. Lowering A.sub.w restricts the growth of bacteria and is accomplished by lowering P, the vapor pressure of water in the food item. P may be depressed by including sufficient amounts of solutes in the food item. The drop in P is in accordance with Raoult's law which states that P=A.sub.w P.sub.o, where A.sub.w is also the ratio of moles of solvent over sum of moles of solute plus solvent, i.e. n.sub.2 divided by (n.sub.1 +n.sub.2), where n.sub.1 =moles solute and n.sub.2 =moles of solvent. For a 1 molal solution of an ideal solute, A.sub.w = P divided by P.sub.o. Thus, n.sub.2 divided by (n.sub.1 +n.sub.2)=55.51 divided by (55.51+1), or 0.9823. Typical solutes employed in foods are sucrose, glucose, invert sugar, salts such as sodium chloride, propylene glycol, incompletely hydrolyzed starches, and the like.
Most bacteria of concern in food preservation require A.sub.w values of 0.90 or greater to grow. There are some halophilic bacteria that grow at A.sub.w values down to 0.75, but they seldom cause food spoilage. Molds, however, will grow at A.sub.w levels down to about 0.65 which is too low for most food to retain an intermediate moisture content. Semimoist foods usually have A.sub.w values between 0.70 and 0.85. An antimycotic is generally included, therefore, to inhibit molds at semimoist levels.
Canadian Patent 1162099, discloses a process for making a filled dough food product which comprises subjecting the filled dough food product (such as ravioli) to a high moisture environment from 70.degree. C.-100.degree. C. to thereby dry the product until the dough portion reaches a moisture content level of 16-19%, then packaging the product to 70.degree. C.-100.degree. C.
U.S. Pat. No. 4,493,850, issued Jan. 15, 1985 to Fioravanti, relates to but does not conform to Canadian Patent No. 1162099. U.S. Pat. No. 4,493,850 discloses subjecting a filled dough food product (such a ravioli) to a high moisture environment at 70.degree. C.-100.degree. C. and subsequently drying the product until the dough portion reaches an average moisture content of 23-28%. The product is then packaged and must be subjected to a temperature of from 70.degree. C.-100.degree. C.
Gaehring, et al., U.S. Pat. No. 4,529,609 (issued July 16, 1985) relates to a pasta product that is dried to a moisture content of no less than about 15% and A.sub.w level of no more than about 0.85. Gaehring, et al. require that their pasta dough comprise finely divided salt. The salt plays a critical role in the successful application of the Gaehring invention. First, the salt allows the use of flour other than durum semolina. It interacts with the protein molecules in the dough at their polar sites modifying the teritiary structure of the proteins which results in increased flexibility. Second, the salt reduces surface tension of the water which enables more complete hydration of the protein and starch granules. Third, the salt reduces the amount of free water (i.e., lowering A.sub.w) which prevents spoilage and results in long shelf stability. As used therein, the term "salt" encompasses any edible highly dissociative A.sub.w -depressing solute that provides electrolytes which associate with the polar sites of the protein contained in the flour.
Doster, et al., U.S. Pat. No. 4,597,976, issued July 1, 1986, describes a ravioli formed by filling sheeted dough (about 0.16 inches thick) with an acidified meat filling. After a steaming step, the ravioli is packaged together with a sauce.
Liggett, et al., U.S. Pat. No. 4,898,744, issued Feb. 6, 1990 disclose a fresh stuffed pasta made from dough that has been sheeted to a thickness of about 0.04 inches. The stuffed pasta is pasteurized before it is packaged and must be stored at 40.degree. F. -50.degree. F.
U.S. Pat. No. 4,915,966, issued Apr. 10, 1990 to Guarneri, teaches a method of making dried pasta having a relative moisture content of about 32% by weight while controlling the A.sub.w at levels equal to or higher than 0.86.
One conventional process previously utilized to obtain longer storage time consists of utilizing special driers. This process, however, proved unsatisfactory. Other attempts such as freezing and overfreezing the stuffed pastas into special cooling equipment; canning of the product and subsequently processing in an autoclave; and using germicide lamps or irradiations, for example gamma rays, emitted by radioactive isotopes, all proved to be impractical and uneconomical.
Generally, the filled food products which have undergone normal drying (18-24 hours at up to 150.degree. F., using 31-32% moisture in both the pasta and filling) can only be stored for short periods of time which varies based on the composition of the stuffing and the conditions under which the product was prepared. However, even if proper drying of the outer casing is achieved, longer term storage would be limited mainly because of the composition of the stuffing. Attempts to overcome this problem are disclosed in U.S. Pat. No. 3,281,248 by Fioravanti, et al., wherein stuffed pasta shells are immersed into a liquid selected from water, broth and a mixture of water and oil, said liquid having a temperature of from 65.degree. to 120.degree. C. for a period of time ranging from 1 to 240 seconds, followed by removing the stuffed shell from the liquid and heating same to temperatures ranging from 70.degree. to 225.degree. C. for a period of time ranging from 30 seconds to 30 minutes. None of these references, however, teaches maintaining freshness in texture, appearance and taste of a pasta product over extended period of time.
It is, therefore, an object of the present invention to provide a filled or stuffed pasta or dough food product that maintains its freshness for extended periods of time at ambient temperature.
Another object of the present invention is to provide a process for preserving stuffed pasta which maintains its shelf life for extended periods of time.